Thermal switch with bimetallic follower for increasing contact wiping pressure



July 18, 1967 L w. BRACKETT 3,331,934

THERMAL SWITCH WITH BIMETALLIC FQLLOWER FOR INCREASING CONTACT WIPING PRESSURE Filed April 15, 1965 5 Sheets-Sheet l I 'l I 4 20/ /2-' /s/ 20 122'v 32 J 14.4

QM W I y 1967 L. w. BRACKETT 3,331,934

I THERMAL SWITCH WITH BIMETALLIC FOLLOWER FOR INCREASING CONTACT WIPING PRESSURE Filed April 15, 1965 5 Sheets-Sheet 2 L. W. BRACKETT July 18, 1967 3,331,934

THERMAL SWITCH WITH BIMETALLIC FOLLOWER FOR INCREASING CONTACT WIPING PRESSURE Filed April 15, 1965 3 Sheets-Sheet 3 United States Patent Mass, assignor to Lynn, Mass., a corporation This is a continuation-in-part of application Ser. No. 107,437, filed May 3, 1961, now abandoned.

The field of this invention is that of electric switches, and the invention relates, more particularly, to circuit breakers in which contacts are opened and closed by snap action of a buckled spring.

Objects of the present invention are to provide breakers of the above type which are highly sensitive, which are reliable, which are of light weight, which always effect a rapid opening of the contacts under overload conditions, which make and break contact with a wiping move ment; which resist any chattering or bouncing of contacts, and which maintains the contacts in pressurable engagement until rapidly opened by the snap action of the spring, and which are of simple and inexpensive and yet rugged construction.

The substance of the invention can be briefly summarized as to characteristic aspects thereof as contemplating a circuit breaker which has, on a frame, an elongate preferably flat spring which is prestressed so as to assume a predetermined longitudinally bowed normal shape, a pair of resilient standards which are secured to the frame and between which the spring is mounted lengthwise, mechanical control means such as a push button actuated operating member for bowing the spring in a sense opposite to its normal shape, a first contact carried by the spring, and an opposite second contact attached to the frame for engagement by the first stressed spring contact.

In one embodiment the distance by which the standards may flex away from each other is limited by a heat expansible wire stretched between the two standards thereby making available a sufficient stress or force, longitudinally of the spring, to maintain it in bowed position but a shape reverse to the said normal shape, until the wire is heated permitting an increase of the distance of the standards.

In another embodiment at least one of -the standards is of bimetal construction and the standards themselves are sufficiently stiff to provide the force necessary to retain the spring in reverse shape and position until a predetermined temperature is reached when deformation of one or both standards permits the spring to assume normal shape.

In an important practical aspect applicable to either of the above-mentioned embodiments, the above-mentioned second contact is attached to the frame by spring means such as to follow, for a limited distance, the first contact carried by the bowed spring. Preferably this frame, or follower contact, spring means is of bimetal construction so that the force with which the second contact follows the first is a function of temperature substantially complementary to the temperature-responsive force holding the bowed spring in reverse position.

These and other objects, and aspects of the substance of the invention, together with various advantages and beneficial results thereof will appear from the following detailed description of several practical embodiments illustrating its novel characteristics.

The description refers to a drawing in which FIG. 1 is a plan view of a circuit breaker according to the invention;

3,331,934 Patented July 18, 1967 FIG. 2 is a section view along line 22 of FIG. 1 showing the circuit breaker in closed position;

FIG. 3 is a section view similar to FIG. 2 showing the circuit breaker in open position;

FIG. 4 is an end view of the circuit breaker shown in FIG. 2;

FIG. 5 is a bottom view of the circuit breaker;

FIG. 6 is a section view at smaller scale similar to FIG. 2 showing an alternative embodiment of the circuit breaker;

FIG. 7 is a section similar to FIG. 6, with the normally open switch mechanism in elevation, of a further embodiment;

FIG. 8 is a section on line 8-8 of FIG. 7;

FIGS. 9 and 10 are elevations similar to FIG. 7, of the switch mechanism according to FIGS. 7 and 8, in normally preclosing and in closed positions, respectively; and

FIGS. 11 and 12 are sections on lines 1111 and 12- 12 of FIGS. 9 and 10, respectively.

Referring to the drawings, a circuitbreaker according to the invention has a fiat supporting base or frame 10 of insulating material such as a synthetic resin. The casing 12, preferably made of thin sheet steel, is substantially U-shaped, includes a top 12.1 and sides 12.2 and 12.3, and has flanges 12.4 and 12.5 extending outwardly from its respective sides for resting on the base 10. The casing also has ears 12.6 which extend from its sides and which are folded into the notches 10.1 of base 10 for securing the casing to the base. It should be understood that preferred casing and base constructions are illustrated but that any effective mounting and protecting means are within the scope of the invention.

As shown in FIGS. 1 to 5, a standard 14 of resilient conductive material having a mounting portion 14.1 is secured near one end of the base 10 by rivets 14.2. The standard has a centrally located aperture 14.3 and is notched as at 14.4 (FIG. 4) near its top.

A similar standard 16 is secured near the opposite end of the base 10 by means of a mounting portion 16.1 and by rivets 16.2, and is provided with a terminal portion 16.3 which extends downwardly through a slot 10.2 (FIG. 5) in the base. The standard 16 has an aperture 16.4 which is substantially aligned with the aperture 14.3 in the standard 14, and has an extension 18 of insulating material secured thereto by screws 18.1. The extension 18 of the standard 16 is notched near its top as at 18.2 in a manner corresponding to the configuration of standard 14.

A flat contact spring 20, of electrically conductive material and having bifurcated ends 20.1 and 20.2 (FIG. 1), is mounted upon the standards 14 and 16 by inserting the spring end bifurcations 20.1, 20.2 in the notches 14.4 and 18.2 in the standards 14 and 16, respectively. The spring carries a contact 22 and is prestressed so that it tends naturally to assume the shape shown in FIG. 3 herein referred to as normal shape.

A heat-expansible member 24, preferably a length of Nichrome wire, is stretched through the apertures 14.3 and 16.4 in the respective standards and is secured therein by means of split, deformable collars 24.1 and 24.2 of electrically conductive material such as copper.

A terminal 28 having a bent attaching portion 28.1 is secured to the base by means of rivets 28.2 so that the terminal portion proper 28.3 extends through the base slot 103. Secured to the attaching portion of the terminal by means of the rivets 28.2 is a substantially S-shaped spring 30, as shown in FIGS. 2 and 3 herein also referred to as follower spring contact means. This spring member supports a second contact 3 2. As shown in FIGS. 1 and 4 particularly, the flat stressed contact spring 20 has a laterally extending portion 20.3 for supporting the contact 22 and the spring contact support 30 is cut away such as at 33.2 whereby the above described first or spring contact 22 and the prest-ressed spring supported or second contact 32 can cooperate for closing a circuit without interference with the Nichrome wire member 24.

The casing 12 has a central aperture 12.7 in which an operating member 34 is slidably mounted, the collar members 34.1 and 34.2 serving to retain the operating member within its mounting aperture.

In this construction, the length of the heat-expansible wire 24 can be adjusted by means of the collars 24.1 and 24.2 so that the resilient standards 14 and 16 are drawn toward each other, thereby compressing the spring ends inwardly for stressing the spring 20 slightly. Since the standards have inherent resilience, they will tend to move away from each other to return to their unrestrained position and will be further biased to move away from each other by reaction of the spring 21). When the push button operating member 32 is depressed for forcing the spring 21} between the standards 14 and 16 into the reverse buckled position shown in FIG. 2, the contact 22 and the contacts 32 are pressurably engaged. Since the standards 14 and 16 are stressed and thereby restrained from outward movement by the Nichrome wiremernber 24, they will hold the spring 21) in this reverse, opposite to normal, buckled position and maintain the breaker in closed circuit position. As thus arranged the breaker circuit extends from the terminal 23 through the spring member 30, the contacts 32 and 22, the spring 20, the standard 14, and the Nichrome wire 24, to the terminal portion-16.3 of the standard 16.

Since the heat-expansible wire 24 is interposed in the breaker circuit, it will be heated in response to a predetermined overload current in the circuit wherein it is connected thereby to expand for releasing the standards for outward movement due to their inherent resilience and the above mentioned bias of the spring member 20.

As the standards move outwardly, the restraint on the buckled spring 20 is gradually released so that it tends to move through an over-center position and to snap into the position shown in FIG. 3. However, as will be readily understood, as the spring 20 moves toward its center or flat position, this movement tends to reduce the pressure of engagement of the contact 22 with the contact 32. This condition of low contact pressure would be undesirable because, when the breaker is subjected to currents just slightly less than critical or when the breaker opens while subjected to vibration, the contacts may chatter or bounce and the resulting arcing will rapidly wear out the contacts.

It is for this reason that the present invention provides contact spring means 30 for the contact 32 so that, to a certain extent, the contact 32 is indeed is induced to follow the contact 22 as the actuation spring 20 moves comparatively slowly towards its center position thereby maintaining pressurable engagement. Though the throw of the follower contact spring 31) is sufficient to greatly even out the contact pressure over the short movement, it is not sufiicient to follow the comparatively large movements of the contact 22 when the spring 20 passes through its unstable over-center position and snaps rapidly to the normal position shown in FIG. 3. Accordingly, a quite sharp breaking of the contacts is produced which minimizes arcing. It will be noted that the spring 30 and the lateral extension provide for wiping contact at 22, 32 both longitudinally and laterally of the spring 20.

While providing the contact 32 with a spring mount in itself yields a substantially uniform contact pressure up to the time 'of opening and thereupon of a rapid break, thepresent invention also contemplates a preferred embodiment in which the spring mount 36 is of a bimetal construction and arranged so as to provide, when heated, a movement of the contact 32 which is complementary to the movement of the contact 22 before the breaker actually opens, and which will thereby tend to, even more perfectly, maintain a steady pressurable engagement of the contacts until the circuit is actually open. As explained above, the spring 31) is in the breaker circuit along with the wire 24 and thus its heating wll occur concurrently with that of the wire 24, without special provisions.

In FIG. '6 there is illustrated an alternative embodiment of circuit breakers according tothis invention. This embodiment includes an insulating base 110 and a casing 112 having a push button operating member 134 slidably mounted therein. This breaker further includes a terminal 123 secured to the base by means of rivets 128.2, and a bimetallic support 131) carrying a contact 132. In this embodiment one standard, indicated at 36, is composed of electrically conductive, bimetallic material having a horizontal mounting portion 36.1 secured to the base 110 V by means of rivets 36.2. Therivets 36.2 also secure a terminal 40 having the mounting portion 40.1 in electrically conductive relation to the standard 36. A corresponding standard 38, which need not be of bimetallic material, is secured to the base by means of rivets 38.2 in spaced relation to the standard 36 and has an insulating piece 39 secured thereto by screws 39.1. The standard 36 and the standard insulating piece 39 are notched at 36.3 and 39.2 in a manner corresponding to the standards 14 and 16 illustrated in FIGS. 1 to 5, and a flat spring having bifurcated ends and carrying the contact 122 is similarly mounted on said standards. Therefore the breaker circuit extends from the terminal 40 through the standard 36, the flat spring 120, the contacts 122 and 132, and the bimetallic support to the terminal 128.

In this construction the operating member 134 can be depressed for moving the flat spring 120 between the standards 36 and 38 into the opposite from normal or reverse buckled position shown in dotted lines in FIG. 6 for pressurably engaging the contacts 122 and 132. The bimetallic standards themselves have sufiicient inherent resilience and are stressed to maintain the spring 121) in its reverse buckled position during periods of normal operation. In this context it should be understood that, as used herein and in the claims, the term stressed as applied to the standards should be interpreted as including both internal stress within the standard itself and stress applied by an outside agent such as the heat responsive wire of the example of FIGS. 1 to 4. 7 When overload current occurs in the breaker circuit according to FIG. 6, the bimetallic standard 36 is heated and will flex outwardly thereby releasing the flat spring 120 for movement through an over-center posit-ion to normally buckled position, as in the construction previously described. The bimetallic contact support 130 is adapted to be correspondingly heated in response to such an overload current as in the first example and will flex upwardly, thereby again tending to maintain pressurable engagement of the contacts 122 and 132 until the spring 120 snaps to its normal buckled position.

The further embodiment now to be described with reference to FIGS. 7 to 12 is a further development of the embodiment described with reference to FIG. 6 and includes various features, especially that of so-called trip free operation which is usually obtainable only with much more complex mechanisms. Parts which occur in essentially identical configuration in FIG. 6 are given the same identification numerals in FIGS. 7 to 12.

FIGS. 7 to 12 show a housing 212 of insulating material which consists of two halves 213, 214, has an actuator or cover portion 215 with metallic sleeve 216 swaged thereto and a supporting base portion 210. The two housing halves are secured together by means of bolts or similar means inserted in perforations 217, 218, 219. Held in suitably shaped and proportioned slits 213.1, 214.1 of the housing halves are terminal 'bars 128 and 140. A standard 138 is fastened to the insulating housing by means of a hook portion 38.1 held to the housing by a screw and nut arrangement 3 8.2 which can be of insulating material and also serves for "adjusting the tension of the standard 138. A second standard 36 is at 36.1

fastened to the terminal bar 140 and, as in FIG. 6, this standard 36 is made of bimetallic material and will bend outwardly on heating up.

The stressed conductive spring means 120 is hinged to the standards 138 and 36 at 39.2 and 36.3, and both standards are stressed sufliciently to maintain the stressed spring means in either of its bowed shapes, as previously described.

A follower spring contact means 130 is suitably fastened, such as by means of a rivet or screw 128.2, to the terminal bar 128. The spring contact means is made preferably but not necessarily of bimetallic material and has a contact 132. If it is bimetallic, spring 130 will bend towards spring 120 on heating up. The terminal bars and standards are suitably confined on shelves and in recesses of the housing. The stressed spring means 126 is normally bowed away from the housing base 210. It is mounted between the free ends of the standards 138 and 36 and has an intermediate contact portion 122 cooperating with the contact 132 of follower spring means 130.

An actuating means 230 is movably mounted on the actuator sleeve 216 and in this embodiment includes a push button 231 and a reciprocating plunger 234 which extends towards the stressed conductive spring 120. A spring 220 is confined between a flange 221 of the push button 231 and inwardly projecting shelf portions 222, 223 of the housing. The reciprocating plunger 234 is guided by means of a pin 311 which is guided in slots 313 and 314 of the respective housing halves 213 and 214. The plunger 234 has an extension 335 that carries a head 336 to which is fastened a yoke 321 with an intermediate neck portion 322 and two depending arms 324 and 325 which reach beyond the stressed spring 120. This yoke is with suitable means fastened, such "s swaged or crimped, to the head 336 and provides at its neck a transverse face 333. The follower spring means 130 has, preferably below its contact 132, a bridge 326 which extends laterally beyond the edges of the follower spring 130.

The stressed conductive spring means 120 has fastened thereto, for example by welding, two retaining means, here clamp fingers 341 and 342. These retaining clamp fingers 341, 342 are so proportioned and mounted that their ends 343, 344. clear the plunger 335 at all times, whereas they contact the face 333 of the yoke 321 when the stressed spring 120 is in the position shown in FIG. 10. As will be explained more in detail hereinbelow with reference to FIGS. 9 and 11, the arms 324, 325 of yoke 321 are sufliciently long to depress the bridge 326 of contact 132 when the plunger is pushed downwardly against the biasing force of spring 220, to separate it from the contact 122 of the stressed spring 1120, even if the latter is in fully downwardly bowed shape.

The plunger 234 is capable of bowing the stressed spring 120 into the reverse position opposite its normal shape, which reverse or opposite position is shown in FIGS. 9 and 10. The biasing force of 220 is unable to counteract the buckling force of the stressed spring 120 as well as the yielding force of the follower spring means 130 so that the head 336 will be move-d upwardly by the bridge 326 and the yoke 321 when the spring 120 is in the normally bowed position as shown in FIGS. 6, 7 and 8. It will be noted that in this position the clamp fingers 343, 349, are moved away from the plunger, releasing the head 336, as shown in FIGS. 7 and 8. 232 is a trip indicator.

. With the bimetallic standard 36 at normal temperature, the stressed spring means 120 is either in the normally or reversely bowed position, depending on the operation of the push button whereas, if standard 36 is hot and bends outwardly as indicated in dot and dash lines in FIG. 10, and the spring 120 is in reverse, contactmaking position, this spring will snap from reverse or 5 oppositely, to the normally bowed or open position of FIGS. 6 and 7.

It will be understood that the push button actuator 231 can be replaced by other means for reciprocating the plunger means 335, for example a toggle arrangement.

As mentioned above, the standards 138 and 36 are stressed sufficiently to maintain the stressed spring means in either bowed shape, so long as standard 36 is in the position shown in full lines in FIG. 10. When 36 moves outwardly into contact opening shape, the stressed spring 120 snaps into the normal contact breaking position of FIG. '7 if it should have been held by the cool standard 36 in the circuit making position of FIGS. 9 and 10.

Instead of the bimetallic standard 36, a wire construction similar to that described above with reference to FIGS. 1 to 5 can be used.

The follower spring means with contact 132 may or may not be made of bimetallic material. In any case it is elastic and tends to make wiping contact at 122 of the stressed spring 120. The construction described permits the spring 130 to be in the normally closed current path of the circuit breaker so that it can be made to bend upwardly with increasing temperature, finally leading to the opening of the circuit.

The operation of the device described above with reference to FIGS. 7 to 12 is as follows.

In open position (FIGS. 7 and 8) the stressed spring 120 is bent upwardly, and the retaining clamp fingers 343, 344 are open permitting the spring 226 to retain the push button Or other actuating means in upper or open'position.

If it is desired to close the breaker, the push button is depressed as shown in FIGS. 9 and 10. The downward movement of the plunger 335 snaps the stressed spring 120 into oppositely bowed position and the clamp fingers move over the face 333 of the head 336. With the push button fully depressed, the depending yoke arms 324, 325 press on the bridge 326 moving the contact 132 of the follower spring means 130 somewhat below its normal position such as to establish a disconnecting gap between contacts 122 and 132. With the standard 36 in normal, cool, condition, the release of the push button permits the two contacts 122 and 132 to close and to establish a current path from terminal through bimetallic standard 36, righthand portion of spring 120, contact 122, contact 132, spring 130 to terminal 128. This position is shown in FIG. 10. The fingers 343, 344 retain the push button in closed position.

If it is desired to open the circuit breaker back into the position shown in FIG. 7, the actuating means is pulled outwardly whereby the clamp fingers 343, 349 are also pulled outwardly and snap the stressed spring 120 into the normally bowed, circuit opening position as shown in FIG. 7. The spring 220 is not able to overcome the stress of 120.

If overheating occurs and the standard 36 bends outwardly as indicated with dot and dash lines in FIG. 10, the spring 120 buckles upwardly against the force of the weaker spring 220, into the position of FIG. 7. If the push button is forced downwardly with standard 36 still hot, the position shown in FIG. 9 with contacts 122 and 132 separated will first occur, keeping the circuit breaker open. If the push button or other actuating device is then released, the spring 120 will immediately buckle upwardly without contact occurring, back into position FIG. 7. It will be evident that the last described operation is that commonly referred to as trip free, namely prohibiting forced closure of the circuit breaker so long as abnormal current condition prevails.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A circuit breaker comprising:

housing means with a supporting base and an actuator portion;

actuating means movably mounted on said actuator portion and including a reciprocating plunger extending towards said base;

a pair of spaced standards each secured at one end to said base; stressed conductive spring means normally bowed away from said base, mounted between the other ends of said standards, and having a contact portion facing the base on the side opposite said plunger, said plunger having head means on an end facing the stressed spring means and being capable of bowing the stressed spring means opposite to said normal shape, said standards being stressed sufficiently to maintain the stressed spring means in either bowed shape; current responsive means for releasing the stress of said standards to allow the stressed spring means to snap from oppositely into normally bowed shape;

follower spring means secured to said support between said spaced standards and having a contact which it tends to press wipingly against said contact portion of the stressed spring means in its oppositely bowed shape; and a clamp means mounted on the stressed spring means for engaging said head means with the normally bowed spring means, and for releasing the head means from the oppositely bowed spring means;

whereby pressurable contact is normally maintained between contact portion and spring contact means, and contact breaks and remains broken with the stressed spring means snapping to and remaining in normally bowed shape until the actuating means moves the stressed spring means from normally to oppositely bowed shape.

2. Circuit breaker according to claim 1 wherein said head means has a flat transverse face on the side opposite the stressed spring means, and wherein said clamp means includes two fingers one on each side of said contact portion with the outer ends fastened to the stressed spring means and with the inner ends distanced from the stressed spring means and adjacent to said head means, such that said inner ends touch said transverse face and clear the plunger portion when the stressed spring means is in normally bowed shape.

3. A circuit breaker comprising:

housing means with a supporting base and an actuator portion;

actuating means movably mounted on said actuator portion and including a reciprocating plunger extending towards said base;

a pair of spaced standards each secured at one end to said base;

stressed conductive spring means normally bowed away from said base, mounted between the other ends of said standards, and having a contact portion facing the base on the side opposite said plunger, said plunger being capable of bowing the stressed spring means opposite to said normal shape, said standards being stressed sufliciently to maintain the stressed spring means in either bowed shape;

current responsive means for releasing the stress of said standards to allow the stressed spring means to snap from oppositely into normally bowed shape; follower spring means secured to said support between said spaced standards and having a contact which it tends to press wipingly against said contact portion of the stressed spring means in its oppositely bowed shape;

means for biasing said plunger away from said stressed spring means with a force less than that exerted by said follower spring means; I

depressor means mounted on said head means and extending toward said follower spring means; and

stop means mounted on and extending from said follower spring means into the path of said depressor means, the depressor means and the stop means being placed and dimensioned such that the depressor means contacts the stop means for disengaging said contact portion of the stressed spring means from said contact of the follower spring means when said plunger moves towards said base after having bowed the spring means into said opposition position;

whereby pressurable contact is normally maintained between contact portion and spring contact means, and contact breaks and remains broken with the stressed spring means snapping to and remaining in normally bowed shape until the actuating means moves the stressed spring means from normally to oppositely bowed shape.

4. Circuit breaker according to claim 3, wherein said depressor means include a yoke having two arms extending towards said base beyond said follower spring means and having an intermediate neck portion that is fastened to said head means, and wherein said stop means include a bridge fastened to and extending laterally from said contact of said follower spring means.

5. A circuit breaker comprising:

flat insulating support means;

a pair of resilient spaced standards each secured at one end to said support means, with the secured ends spaced from each other and the other ends freely projecting from the spaced secured ends, respectively, one of the standards being wholly conductive and the projecting end of one of the standards being formed of insulating material, the other end being metallic and forming a terminal at the support means, and the secured end of one of the standards forming a terminal at the support means;

stressed conductive spring means normally assuming a shape bowed away from the support means, mounted between the projecting ends of the standards and having a contact portion on the side of the support means;

mechanical control means adopted to bow said stressed spring means opposite to its normal shape, said standards being stressed sufficiently to maintain the stressed spring means in either bowed shape;

current responsive control means for releasing the stress of said standards to allow the stressed spring means to snap from oppositely into normally bowed shape, including heat expansible wire means interposed in the closed breaker circuit, extending between said standards, and normally maintaining said stressed spring means in said oppositely bowed shape, while upon expansion allowing the standards to release the stressed spring means to bow into normal shape; and

bimetallic follower spring contact means secured to said support means between said secured ends of the standards, interposed in the circuit breaker current path, and tending when heated to exert increasing wiping pressure against said contact portion of the oppositely bowed stressed spring means;

whereby contact is broken between the contact portion of the oppositely bowed stressed spring means and the follower contact means and, while the control means bow the stressed spring means into oppositely bowed shape, wiping contact is maintained between contact portion and follower contact means.

6. Circuit breaker according to claim 5 wherein said stressed spring means is elongate and has near its apex a laterally extending portion constituting said contact portion, and wherein said follower spring contact means is on said support laterally displaced relatively to the stressed spring means and wire means, capable of reaching said contact.

7. A circuit breaker comprising:

a fiat insulating support means;

a pair of resilient spaced standards each secured at one end to said support means, with the secured ends spaced from each other and the other ends freely projecting from the spaced secured ends, respectively, one of the standards being wholly conductive and forming a terminal at the support means, and the projecting end of one of the standards being formed of insulating material, the other end being metallic, and the secured end of one of the standards forming a terminal at the support means;

stressed conductive spring means normally assuming a shape bowed away from the support means, mounted between the projecting ends of the standards and having a contact portion on the side of the support means;

mechanical control means adapted to bow said stressed spring means opposite to its normal shape, said standards being stressed sufliciently to maintain the stressed spring means in either bowed shape;

current responsive control means for releasing the stress of said standards to allow the stressed spring means to snap from oppositely into normally bowed shape, including bimetallic heat sensitive means constituting a portion of said wholly conductive standard interposed in the closed breaker circuit and normally maintaining said stressed spring means in oppositely bowed shape while upon flexion allowing the stressed spring contact means to bow into normal shape; and bimetallic follower spring contact means secured to said support means between said secured ends of the standards, interposed in the circuit breaker current path, and tending when heated to exert increasing wiping pressure against said contact portion of the oppositely bowed stressed spring means;

whereby contact is broken between the contact portion of the oppositely bowed stressed spring means and the follower contact means and, while the control means bow the stressed spring means into oppositely bowed shape, wiping contact is maintained between contact portion and follower contact means.

8. A circuit breaker comprising:

housing means with a supporting base and an actuator portion;

a pair of spaced standards each secured at one end to said base, one of said standards having terminal means and being of bimetallic construction such as to swing its other end outwardly upon being heated;

actuating means movably mounted on said actuator portion and including a reciprocating plunger extending with one end towards, and being biased away from, said base, having head means on said extending end of the plunger, and having fastened thereto depressor means extending beyond the head means;

stressed conductive spring means normally bowed away from said base, mounted between the other ends of said standards, having a contact portion adjacent said depressor means, facing the base on the side opposite said head means, and capable of being bowed by the head means opposite to said normal shape, said standards being stressed sufliciently to maintain the stressed spring means in either bowed shape against said bias of the plunger, and said stressed spring means carrying, one at each side of and facing said head means, two clamp fingers distanced from said plunger with their inner ends and fastened to the stressed spring means with their outer ends such as to engage the head with the stressed spring means in said opposite shape and thereupon capable of snapping the stressed spring means into normal shape on pulling the plunger away from the base,

current responsive means for releasing the stress of said standards to allow the stressed spring means to snap from oppositely into normally bowed shape; and

follower spring means secured at one end to said support between said spaced standards, having at the other end a contact which it tends to press wipingly against said contact portion of the stressed spring means to contact it wipingly in its oppositely bowed shape, having at said other end a laterally extending bridge capable of being engaged by said depressor means, and exerting a force capable of overcoming the bias of said actuating means but incapable of bowing said stressed spring means.

References Cited UNITED STATES PATENTS 1,215,665 2/1917 Landis 200-67 1,803,982 5/1931 Thomas.

1,899,558 2/1933 Cohn et al.

1,970,514 8/1934 Laubenfels 200-137 2,133,309 10/ 1938 Schmidinger 20067 X 2,379,602 7/1945 Stickel 200-113 X 2,441,979 5/1948 Schmidinger et al. 200-122 X 2,906,835 9/1959 Schmidinger 200-122 X 3,004,129 10/1961 Koci 200113 X 3,025,373 3/1962 Bullis 200-1 13 3,056,871 10/ 1962 Broekhuysen.

3,187,145 6/1965 Grabinski 200113 FOREIGN PATENTS 1,085,267 1/1955 France.

BERNARD A. GILHEANY, Primary Examiner. H. A. LEWITTER, Assistant Examiner. 

1. A CIRCUIT BREAKER COMPRISING: HOUSING MEANS WITH A SUPPORTING BASE AND AN ACTUATOR PORTION; ACTUATING MEANS MOVABLY MOUNTED ON SAID ACTUATOR PORTION AND INCLUDING A RECIPROCATING PLUNGER EXTENDING TOWARDS SAID BASE; A PAIR OF SPACED STANDARDS EACH SECURED AT ONE END TO SAID BASE; STRESSED CONDUCTIVE SPRING MEANS NORMALLY BOWED AWAY FROM SAID BASE, MOUNTED BETWEEN THE OTHER ENDS OF SAID STANDARDS, AND HAVING A CONTACT PORTION FACING THE BASE ON THE SIDE OPPOSITE SAID PLUNGER, SAID PLUNGER HAVING HEAD MEANS ON AN END FACING THE STRESSED SPRING MEANS AND BEING CAPABLE OF BOWING THE STRESSED SPRING MEANS OPPOSITE TO SAID NORMAL SHAPE, SAID STANDARDS BEING STRESSED SUFFICIENTLY TO MAINTAIN THE STRESSED SPRING MEANS IN EITHER BOWED SHAPE; CURRENT RESPONSIVE MEANS FOR RELEASING THE STRESS OF SAID STANDARDS TO ALLOW THE STRESSED SPRING MEANS TO SNAP FROM OPPOSITELY INTO NORMALLY BOWED SHAPE; FOLLOWER SPRING MEANS SECURED TO SAID SUPPORT BETWEEN SAID SPACED STANDARDS AND HAVING A CONTACT WHICH IT TENDS TO WIPINGLY AGAINST SAID CONTACT PORTION OF THE STRESSED SPRING MEANS IN ITS OPPOSITELY BOWED SHAPE; AND CLAMP MEANS MOUNTED ON THE STRESSED SPRING MEANS FOR ENGAGING SAID HEAD MEANS WITH THE NORMALLY BOWED SPRING MEANS, AND FOR RELEASING THE HEAD MEANS FROM THE OPPOSITELY BOWED SPRING MEANS; WHEREBY PRESSURABLE CONTACT IS NORMALLY MAINTAINED BETWEEN CONTACT PORTION AND SPRING CONTACT MEANS, AND CONTACT BREAKS AND REMAINS BROKEN WITH THE STRESSED SPRING MEANS SNAPPING TO AND REMAINING IN NORMALLY BOWED SHAPE UNTIL THE ACTUATING MEANS MOVES THE STRESSED SPRING MEANS FROM NORMALLY TO OPPOSITELY BOWED SHAPE. 